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			<div id="docsContent">
				
<p><a href="../../../editdocs#docs/tasks/configure-pod-container/configure-liveness-readiness-probes.md" id="editPageButton">Edit This Page</a></p>

<h1>Configure Liveness and Readiness Probes</h1>




<p>This page shows how to configure liveness and readiness probes for Containers.</p>

<p>The <a href="../../../admin/kubelet/index.html">kubelet</a> uses liveness probes to know when to
restart a Container. For example, liveness probes could catch a deadlock,
where an application is running, but unable to make progress. Restarting a
Container in such a state can help to make the application more available
despite bugs.</p>

<p>The kubelet uses readiness probes to know when a Container is ready to start
accepting traffic. A Pod is considered ready when all of its Containers are ready.
One use of this signal is to control which Pods are used as backends for Services.
When a Pod is not ready, it is removed from Service load balancers.</p>











<ul id="markdown-toc">










<li><a href="../../../user-guide/liveness/index.html#before-you-begin">Before you begin</a></li>












<li><a href="../../../user-guide/liveness/index.html#define-a-liveness-command">Define a liveness command</a></li>




<li><a href="../../../user-guide/liveness/index.html#define-a-liveness-http-request">Define a liveness HTTP request</a></li>




<li><a href="../../../user-guide/liveness/index.html#define-a-tcp-liveness-probe">Define a TCP liveness probe</a></li>




<li><a href="../../../user-guide/liveness/index.html#use-a-named-port">Use a named port</a></li>




<li><a href="../../../user-guide/liveness/index.html#define-readiness-probes">Define readiness probes</a></li>




<li><a href="../../../user-guide/liveness/index.html#configure-probes">Configure Probes</a></li>




























<li><a href="../../../user-guide/liveness/index.html#what-s-next">What's next</a></li>



</ul>



<h2 id="before-you-begin">Before you begin</h2>
<p>You need to have a Kubernetes cluster, and the kubectl command-line tool must
be configured to communicate with your cluster. If you do not already have a
cluster, you can create one by using
<a href="../../../getting-started-guides/minikube">Minikube</a>,
or you can use one of these Kubernetes playgrounds:</p>

<ul>
<li><a href="https://www.katacoda.com/courses/kubernetes/playground" target="_blank">Katacoda</a></li>
<li><a href="http://labs.play-with-k8s.com/" target="_blank">Play with Kubernetes</a></li>
</ul>
 

<p>To check the version, enter <code>kubectl version</code>.</p>




<h2 id="define-a-liveness-command">Define a liveness command</h2>

<p>Many applications running for long periods of time eventually transition to
broken states, and cannot recover except by being restarted. Kubernetes provides
liveness probes to detect and remedy such situations.</p>

<p>In this exercise, you create a Pod that runs a Container based on the
<code>k8s.gcr.io/busybox</code> image. Here is the configuration file for the Pod:</p>

<table class="includecode" id="exec-liveness-yaml">
    <thead>
        <tr>
            <th>
                <a href="https://github.com/kubernetes/website/blob/master/content/en/docs/tasks/configure-pod-container/exec-liveness.yaml" download="exec-liveness.yaml">
                    <code>exec-liveness.yaml docs/tasks/configure-pod-container</code>
                </a>
                <img src="../../../../images/copycode.svg" style="max-height:24px" onclick="copyCode('exec-liveness-yaml')" title="Copy exec-liveness.yaml to clipboard">
            </th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td><div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-yaml" data-lang="yaml">apiVersion:<span style="color:#bbb"> </span>v1<span style="color:#bbb">
</span><span style="color:#bbb"></span>kind:<span style="color:#bbb"> </span>Pod<span style="color:#bbb">
</span><span style="color:#bbb"></span>metadata:<span style="color:#bbb">
</span><span style="color:#bbb">  </span>labels:<span style="color:#bbb">
</span><span style="color:#bbb">    </span>test:<span style="color:#bbb"> </span>liveness<span style="color:#bbb">
</span><span style="color:#bbb">  </span>name:<span style="color:#bbb"> </span>liveness-exec<span style="color:#bbb">
</span><span style="color:#bbb"></span>spec:<span style="color:#bbb">
</span><span style="color:#bbb">  </span>containers:<span style="color:#bbb">
</span><span style="color:#bbb">  </span>-<span style="color:#bbb"> </span>name:<span style="color:#bbb"> </span>liveness<span style="color:#bbb">
</span><span style="color:#bbb">    </span>image:<span style="color:#bbb"> </span>k8s.gcr.io/busybox<span style="color:#bbb">
</span><span style="color:#bbb">    </span>args:<span style="color:#bbb">
</span><span style="color:#bbb">    </span>-<span style="color:#bbb"> </span>/bin/sh<span style="color:#bbb">
</span><span style="color:#bbb">    </span>-<span style="color:#bbb"> </span>-c<span style="color:#bbb">
</span><span style="color:#bbb">    </span>-<span style="color:#bbb"> </span>touch<span style="color:#bbb"> </span>/tmp/healthy;<span style="color:#bbb"> </span>sleep<span style="color:#bbb"> </span><span style="color:#666">30</span>;<span style="color:#bbb"> </span>rm<span style="color:#bbb"> </span>-rf<span style="color:#bbb"> </span>/tmp/healthy;<span style="color:#bbb"> </span>sleep<span style="color:#bbb"> </span><span style="color:#666">600</span><span style="color:#bbb">
</span><span style="color:#bbb">    </span>livenessProbe:<span style="color:#bbb">
</span><span style="color:#bbb">      </span>exec:<span style="color:#bbb">
</span><span style="color:#bbb">        </span>command:<span style="color:#bbb">
</span><span style="color:#bbb">        </span>-<span style="color:#bbb"> </span>cat<span style="color:#bbb">
</span><span style="color:#bbb">        </span>-<span style="color:#bbb"> </span>/tmp/healthy<span style="color:#bbb">
</span><span style="color:#bbb">      </span>initialDelaySeconds:<span style="color:#bbb"> </span><span style="color:#666">5</span><span style="color:#bbb">
</span><span style="color:#bbb">      </span>periodSeconds:<span style="color:#bbb"> </span><span style="color:#666">5</span><span style="color:#bbb">
</span><span style="color:#bbb"></span></code></pre></div>  </td>
        </tr>
    </tbody>
</table>

<p>In the configuration file, you can see that the Pod has a single Container.
The <code>periodSeconds</code> field specifies that the kubelet should perform a liveness
probe every 5 seconds. The <code>initialDelaySeconds</code> field tells the kubelet that it
should wait 5 second before performing the first probe. To perform a probe, the
kubelet executes the command <code>cat /tmp/healthy</code> in the Container. If the
command succeeds, it returns 0, and the kubelet considers the Container to be alive and
healthy. If the command returns a non-zero value, the kubelet kills the Container
and restarts it.</p>

<p>When the Container starts, it executes this command:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">/bin/sh -c <span style="color:#b44">&#34;touch /tmp/healthy; sleep 30; rm -rf /tmp/healthy; sleep 600&#34;</span></code></pre></div>
<p>For the first 30 seconds of the Container&rsquo;s life, there is a <code>/tmp/healthy</code> file.
So during the first 30 seconds, the command <code>cat /tmp/healthy</code> returns a success
code. After 30 seconds, <code>cat /tmp/healthy</code> returns a failure code.</p>

<p>Create the Pod:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">kubectl create -f https://k8s.io/docs/tasks/configure-pod-container/exec-liveness.yaml</code></pre></div>
<p>Within 30 seconds, view the Pod events:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">kubectl describe pod liveness-exec</code></pre></div>
<p>The output indicates that no liveness probes have failed yet:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">FirstSeen    LastSeen    Count   From            SubobjectPath           Type        Reason      Message
--------- --------    -----   ----            -------------           --------    ------      -------
24s       24s     <span style="color:#666">1</span>   <span style="color:#666">{</span>default-scheduler <span style="color:#666">}</span>                    Normal      Scheduled   Successfully assigned liveness-exec to worker0
23s       23s     <span style="color:#666">1</span>   <span style="color:#666">{</span>kubelet worker0<span style="color:#666">}</span>   spec.containers<span style="color:#666">{</span>liveness<span style="color:#666">}</span>   Normal      Pulling     pulling image <span style="color:#b44">&#34;k8s.gcr.io/busybox&#34;</span>
23s       23s     <span style="color:#666">1</span>   <span style="color:#666">{</span>kubelet worker0<span style="color:#666">}</span>   spec.containers<span style="color:#666">{</span>liveness<span style="color:#666">}</span>   Normal      Pulled      Successfully pulled image <span style="color:#b44">&#34;k8s.gcr.io/busybox&#34;</span>
23s       23s     <span style="color:#666">1</span>   <span style="color:#666">{</span>kubelet worker0<span style="color:#666">}</span>   spec.containers<span style="color:#666">{</span>liveness<span style="color:#666">}</span>   Normal      Created     Created container with docker id 86849c15382e; Security:<span style="color:#666">[</span><span style="color:#b8860b">seccomp</span><span style="color:#666">=</span>unconfined<span style="color:#666">]</span>
23s       23s     <span style="color:#666">1</span>   <span style="color:#666">{</span>kubelet worker0<span style="color:#666">}</span>   spec.containers<span style="color:#666">{</span>liveness<span style="color:#666">}</span>   Normal      Started     Started container with docker id 86849c15382e</code></pre></div>
<p>After 35 seconds, view the Pod events again:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">kubectl describe pod liveness-exec</code></pre></div>
<p>At the bottom of the output, there are messages indicating that the liveness
probes have failed, and the containers have been killed and recreated.</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">FirstSeen LastSeen    Count   From            SubobjectPath           Type        Reason      Message
--------- --------    -----   ----            -------------           --------    ------      -------
37s       37s     <span style="color:#666">1</span>   <span style="color:#666">{</span>default-scheduler <span style="color:#666">}</span>                    Normal      Scheduled   Successfully assigned liveness-exec to worker0
36s       36s     <span style="color:#666">1</span>   <span style="color:#666">{</span>kubelet worker0<span style="color:#666">}</span>   spec.containers<span style="color:#666">{</span>liveness<span style="color:#666">}</span>   Normal      Pulling     pulling image <span style="color:#b44">&#34;k8s.gcr.io/busybox&#34;</span>
36s       36s     <span style="color:#666">1</span>   <span style="color:#666">{</span>kubelet worker0<span style="color:#666">}</span>   spec.containers<span style="color:#666">{</span>liveness<span style="color:#666">}</span>   Normal      Pulled      Successfully pulled image <span style="color:#b44">&#34;k8s.gcr.io/busybox&#34;</span>
36s       36s     <span style="color:#666">1</span>   <span style="color:#666">{</span>kubelet worker0<span style="color:#666">}</span>   spec.containers<span style="color:#666">{</span>liveness<span style="color:#666">}</span>   Normal      Created     Created container with docker id 86849c15382e; Security:<span style="color:#666">[</span><span style="color:#b8860b">seccomp</span><span style="color:#666">=</span>unconfined<span style="color:#666">]</span>
36s       36s     <span style="color:#666">1</span>   <span style="color:#666">{</span>kubelet worker0<span style="color:#666">}</span>   spec.containers<span style="color:#666">{</span>liveness<span style="color:#666">}</span>   Normal      Started     Started container with docker id 86849c15382e
2s        2s      <span style="color:#666">1</span>   <span style="color:#666">{</span>kubelet worker0<span style="color:#666">}</span>   spec.containers<span style="color:#666">{</span>liveness<span style="color:#666">}</span>   Warning     Unhealthy   Liveness probe failed: cat: can<span style="color:#b44">&#39;t open &#39;</span>/tmp/healthy<span style="">&#39;</span>: No such file or directory</code></pre></div>
<p>Wait another 30 seconds, and verify that the Container has been restarted:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">kubectl get pod liveness-exec</code></pre></div>
<p>The output shows that <code>RESTARTS</code> has been incremented:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">NAME            READY     STATUS    RESTARTS   AGE
liveness-exec   <span style="color:#666">1</span>/1       Running   <span style="color:#666">1</span>          1m</code></pre></div>
<h2 id="define-a-liveness-http-request">Define a liveness HTTP request</h2>

<p>Another kind of liveness probe uses an HTTP GET request. Here is the configuration
file for a Pod that runs a container based on the <code>k8s.gcr.io/liveness</code>
image.</p>

<table class="includecode" id="http-liveness-yaml">
    <thead>
        <tr>
            <th>
                <a href="https://github.com/kubernetes/website/blob/master/content/en/docs/tasks/configure-pod-container/http-liveness.yaml" download="http-liveness.yaml">
                    <code>http-liveness.yaml docs/tasks/configure-pod-container</code>
                </a>
                <img src="../../../../images/copycode.svg" style="max-height:24px" onclick="copyCode('http-liveness-yaml')" title="Copy http-liveness.yaml to clipboard">
            </th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td><div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-yaml" data-lang="yaml">apiVersion:<span style="color:#bbb"> </span>v1<span style="color:#bbb">
</span><span style="color:#bbb"></span>kind:<span style="color:#bbb"> </span>Pod<span style="color:#bbb">
</span><span style="color:#bbb"></span>metadata:<span style="color:#bbb">
</span><span style="color:#bbb">  </span>labels:<span style="color:#bbb">
</span><span style="color:#bbb">    </span>test:<span style="color:#bbb"> </span>liveness<span style="color:#bbb">
</span><span style="color:#bbb">  </span>name:<span style="color:#bbb"> </span>liveness-http<span style="color:#bbb">
</span><span style="color:#bbb"></span>spec:<span style="color:#bbb">
</span><span style="color:#bbb">  </span>containers:<span style="color:#bbb">
</span><span style="color:#bbb">  </span>-<span style="color:#bbb"> </span>name:<span style="color:#bbb"> </span>liveness<span style="color:#bbb">
</span><span style="color:#bbb">    </span>image:<span style="color:#bbb"> </span>k8s.gcr.io/liveness<span style="color:#bbb">
</span><span style="color:#bbb">    </span>args:<span style="color:#bbb">
</span><span style="color:#bbb">    </span>-<span style="color:#bbb"> </span>/server<span style="color:#bbb">
</span><span style="color:#bbb">    </span>livenessProbe:<span style="color:#bbb">
</span><span style="color:#bbb">      </span>httpGet:<span style="color:#bbb">
</span><span style="color:#bbb">        </span>path:<span style="color:#bbb"> </span>/healthz<span style="color:#bbb">
</span><span style="color:#bbb">        </span>port:<span style="color:#bbb"> </span><span style="color:#666">8080</span><span style="color:#bbb">
</span><span style="color:#bbb">        </span>httpHeaders:<span style="color:#bbb">
</span><span style="color:#bbb">        </span>-<span style="color:#bbb"> </span>name:<span style="color:#bbb"> </span>X-Custom-Header<span style="color:#bbb">
</span><span style="color:#bbb">          </span>value:<span style="color:#bbb"> </span>Awesome<span style="color:#bbb">
</span><span style="color:#bbb">      </span>initialDelaySeconds:<span style="color:#bbb"> </span><span style="color:#666">3</span><span style="color:#bbb">
</span><span style="color:#bbb">      </span>periodSeconds:<span style="color:#bbb"> </span><span style="color:#666">3</span><span style="color:#bbb">
</span><span style="color:#bbb"></span></code></pre></div>  </td>
        </tr>
    </tbody>
</table>

<p>In the configuration file, you can see that the Pod has a single Container.
The <code>periodSeconds</code> field specifies that the kubelet should perform a liveness
probe every 3 seconds. The <code>initialDelaySeconds</code> field tells the kubelet that it
should wait 3 seconds before performing the first probe. To perform a probe, the
kubelet sends an HTTP GET request to the server that is running in the Container
and listening on port 8080. If the handler for the server&rsquo;s <code>/healthz</code> path
returns a success code, the kubelet considers the Container to be alive and
healthy. If the handler returns a failure code, the kubelet kills the Container
and restarts it.</p>

<p>Any code greater than or equal to 200 and less than 400 indicates success. Any
other code indicates failure.</p>

<p>You can see the source code for the server in
<a href="https://github.com/kubernetes/kubernetes/blob/master/test/images/liveness/server.go" target="_blank">server.go</a>.</p>

<p>For the first 10 seconds that the Container is alive, the <code>/healthz</code> handler
returns a status of 200. After that, the handler returns a status of 500.</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-go" data-lang="go">http.HandleFunc(<span style="color:#b44">&#34;/healthz&#34;</span>, <span style="color:#a2f;font-weight:bold">func</span>(w http.ResponseWriter, r <span style="color:#666">*</span>http.Request) {
    duration <span style="color:#666">:=</span> time.Now().Sub(started)
    <span style="color:#a2f;font-weight:bold">if</span> duration.Seconds() &gt; <span style="color:#666">10</span> {
        w.WriteHeader(<span style="color:#666">500</span>)
        w.Write([]<span style="color:#a2f">byte</span>(fmt.Sprintf(<span style="color:#b44">&#34;error: %v&#34;</span>, duration.Seconds())))
    } <span style="color:#a2f;font-weight:bold">else</span> {
        w.WriteHeader(<span style="color:#666">200</span>)
        w.Write([]<span style="color:#a2f">byte</span>(<span style="color:#b44">&#34;ok&#34;</span>))
    }
})</code></pre></div>
<p>The kubelet starts performing health checks 3 seconds after the Container starts.
So the first couple of health checks will succeed. But after 10 seconds, the health
checks will fail, and the kubelet will kill and restart the Container.</p>

<p>To try the HTTP liveness check, create a Pod:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">kubectl create -f https://k8s.io/docs/tasks/configure-pod-container/http-liveness.yaml</code></pre></div>
<p>After 10 seconds, view Pod events to verify that liveness probes have failed and
the Container has been restarted:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">kubectl describe pod liveness-http</code></pre></div>
<h2 id="define-a-tcp-liveness-probe">Define a TCP liveness probe</h2>

<p>A third type of liveness probe uses a TCP Socket. With this configuration, the
kubelet will attempt to open a socket to your container on the specified port.
If it can establish a connection, the container is considered healthy, if it
can’t it is considered a failure.</p>

<table class="includecode" id="tcp-liveness-readiness-yaml">
    <thead>
        <tr>
            <th>
                <a href="https://github.com/kubernetes/website/blob/master/content/en/docs/tasks/configure-pod-container/tcp-liveness-readiness.yaml" download="tcp-liveness-readiness.yaml">
                    <code>tcp-liveness-readiness.yaml docs/tasks/configure-pod-container</code>
                </a>
                <img src="../../../../images/copycode.svg" style="max-height:24px" onclick="copyCode('tcp-liveness-readiness-yaml')" title="Copy tcp-liveness-readiness.yaml to clipboard">
            </th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td><div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-yaml" data-lang="yaml">apiVersion:<span style="color:#bbb"> </span>v1<span style="color:#bbb">
</span><span style="color:#bbb"></span>kind:<span style="color:#bbb"> </span>Pod<span style="color:#bbb">
</span><span style="color:#bbb"></span>metadata:<span style="color:#bbb">
</span><span style="color:#bbb">  </span>name:<span style="color:#bbb"> </span>goproxy<span style="color:#bbb">
</span><span style="color:#bbb">  </span>labels:<span style="color:#bbb">
</span><span style="color:#bbb">    </span>app:<span style="color:#bbb"> </span>goproxy<span style="color:#bbb">
</span><span style="color:#bbb"></span>spec:<span style="color:#bbb">
</span><span style="color:#bbb">  </span>containers:<span style="color:#bbb">
</span><span style="color:#bbb">  </span>-<span style="color:#bbb"> </span>name:<span style="color:#bbb"> </span>goproxy<span style="color:#bbb">
</span><span style="color:#bbb">    </span>image:<span style="color:#bbb"> </span>k8s.gcr.io/goproxy:<span style="color:#666">0.1</span><span style="color:#bbb">
</span><span style="color:#bbb">    </span>ports:<span style="color:#bbb">
</span><span style="color:#bbb">    </span>-<span style="color:#bbb"> </span>containerPort:<span style="color:#bbb"> </span><span style="color:#666">8080</span><span style="color:#bbb">
</span><span style="color:#bbb">    </span>readinessProbe:<span style="color:#bbb">
</span><span style="color:#bbb">      </span>tcpSocket:<span style="color:#bbb">
</span><span style="color:#bbb">        </span>port:<span style="color:#bbb"> </span><span style="color:#666">8080</span><span style="color:#bbb">
</span><span style="color:#bbb">      </span>initialDelaySeconds:<span style="color:#bbb"> </span><span style="color:#666">5</span><span style="color:#bbb">
</span><span style="color:#bbb">      </span>periodSeconds:<span style="color:#bbb"> </span><span style="color:#666">10</span><span style="color:#bbb">
</span><span style="color:#bbb">    </span>livenessProbe:<span style="color:#bbb">
</span><span style="color:#bbb">      </span>tcpSocket:<span style="color:#bbb">
</span><span style="color:#bbb">        </span>port:<span style="color:#bbb"> </span><span style="color:#666">8080</span><span style="color:#bbb">
</span><span style="color:#bbb">      </span>initialDelaySeconds:<span style="color:#bbb"> </span><span style="color:#666">15</span><span style="color:#bbb">
</span><span style="color:#bbb">      </span>periodSeconds:<span style="color:#bbb"> </span><span style="color:#666">20</span><span style="color:#bbb">
</span><span style="color:#bbb"></span></code></pre></div>  </td>
        </tr>
    </tbody>
</table>

<p>As you can see, configuration for a TCP check is quite similar to an HTTP check.
This example uses both readiness and liveness probes. The kubelet will send the
first readiness probe 5 seconds after the container starts. This will attempt to
connect to the <code>goproxy</code> container on port 8080. If the probe succeeds, the pod
will be marked as ready. The kubelet will continue to run this check every 10
seconds.</p>

<p>In addition to the readiness probe, this configuration includes a liveness probe.
The kubelet will run the first liveness probe 15 seconds after the container
starts. Just like the readiness probe, this will attempt to connect to the
<code>goproxy</code> container on port 8080. If the liveness probe fails, the container
will be restarted.</p>

<p>To try the TCP liveness check, create a Pod:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">kubectl create -f https://k8s.io/docs/tasks/configure-pod-container/tcp-liveness-readiness.yaml</code></pre></div>
<p>After 15 seconds, view Pod events to verify that liveness probes:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">kubectl describe pod goproxy</code></pre></div>
<h2 id="use-a-named-port">Use a named port</h2>

<p>You can use a named
<a href="../../../reference/generated/kubernetes-api/v1.11/index.html#containerport-v1-core">ContainerPort</a>
for HTTP or TCP liveness checks:</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-yaml" data-lang="yaml">ports:<span style="color:#bbb">
</span><span style="color:#bbb"></span>-<span style="color:#bbb"> </span>name:<span style="color:#bbb"> </span>liveness-port<span style="color:#bbb">
</span><span style="color:#bbb">  </span>containerPort:<span style="color:#bbb"> </span><span style="color:#666">8080</span><span style="color:#bbb">
</span><span style="color:#bbb">  </span>hostPort:<span style="color:#bbb"> </span><span style="color:#666">8080</span><span style="color:#bbb">
</span><span style="color:#bbb">
</span><span style="color:#bbb"></span>livenessProbe:<span style="color:#bbb">
</span><span style="color:#bbb">  </span>httpGet:<span style="color:#bbb">
</span><span style="color:#bbb">    </span>path:<span style="color:#bbb"> </span>/healthz<span style="color:#bbb">
</span><span style="color:#bbb">    </span>port:<span style="color:#bbb"> </span>liveness-port</code></pre></div>
<h2 id="define-readiness-probes">Define readiness probes</h2>

<p>Sometimes, applications are temporarily unable to serve traffic.
For example, an application might need to load large data or configuration
files during startup. In such cases, you don&rsquo;t want to kill the application,
but you don’t want to send it requests either. Kubernetes provides
readiness probes to detect and mitigate these situations. A pod with containers
reporting that they are not ready does not receive traffic through Kubernetes
Services.</p>

<p>Readiness probes are configured similarly to liveness probes. The only difference
is that you use the <code>readinessProbe</code> field instead of the <code>livenessProbe</code> field.</p>
<div class="highlight"><pre style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-yaml" data-lang="yaml">readinessProbe:<span style="color:#bbb">
</span><span style="color:#bbb">  </span>exec:<span style="color:#bbb">
</span><span style="color:#bbb">    </span>command:<span style="color:#bbb">
</span><span style="color:#bbb">    </span>-<span style="color:#bbb"> </span>cat<span style="color:#bbb">
</span><span style="color:#bbb">    </span>-<span style="color:#bbb"> </span>/tmp/healthy<span style="color:#bbb">
</span><span style="color:#bbb">  </span>initialDelaySeconds:<span style="color:#bbb"> </span><span style="color:#666">5</span><span style="color:#bbb">
</span><span style="color:#bbb">  </span>periodSeconds:<span style="color:#bbb"> </span><span style="color:#666">5</span></code></pre></div>
<p>Configuration for HTTP and TCP readiness probes also remains identical to
liveness probes.</p>

<p>Readiness and liveness probes can be used in parallel for the same container.
Using both can ensure that traffic does not reach a container that is not ready
for it, and that containers are restarted when they fail.</p>

<h2 id="configure-probes">Configure Probes</h2>

<p><a href="../../../reference/generated/kubernetes-api/v1.11/index.html#probe-v1-core">Probes</a> have a number of fields that
you can use to more precisely control the behavior of liveness and readiness
checks:</p>

<ul>
<li><code>initialDelaySeconds</code>: Number of seconds after the container has started
before liveness or readiness probes are initiated.</li>
<li><code>periodSeconds</code>: How often (in seconds) to perform the probe. Default to 10
seconds. Minimum value is 1.</li>
<li><code>timeoutSeconds</code>: Number of seconds after which the probe times out. Defaults
to 1 second. Minimum value is 1.</li>
<li><code>successThreshold</code>: Minimum consecutive successes for the probe to be
considered successful after having failed. Defaults to 1. Must be 1 for
liveness. Minimum value is 1.</li>
<li><code>failureThreshold</code>: When a Pod starts and the probe fails, Kubernetes will
try <code>failureThreshold</code> times before giving up. Giving up in case of liveness probe means restarting the Pod. In case of readiness probe the Pod will be marked Unready.
Defaults to 3. Minimum value is 1.</li>
</ul>

<p><a href="../../../reference/generated/kubernetes-api/v1.11/index.html#httpgetaction-v1-core">HTTP probes</a>
have additional fields that can be set on <code>httpGet</code>:</p>

<ul>
<li><code>host</code>: Host name to connect to, defaults to the pod IP. You probably want to
set &ldquo;Host&rdquo; in httpHeaders instead.</li>
<li><code>scheme</code>: Scheme to use for connecting to the host (HTTP or HTTPS). Defaults to HTTP.</li>
<li><code>path</code>: Path to access on the HTTP server.</li>
<li><code>httpHeaders</code>: Custom headers to set in the request. HTTP allows repeated headers.</li>
<li><code>port</code>: Name or number of the port to access on the container. Number must be
in the range 1 to 65535.</li>
</ul>

<p>For an HTTP probe, the kubelet sends an HTTP request to the specified path and
port to perform the check. The kubelet sends the probe to the pod’s IP address,
unless the address is overridden by the optional <code>host</code> field in <code>httpGet</code>. If
<code>scheme</code> field is set to <code>HTTPS</code>, the kubelet sends an HTTPS request skipping the
certificate verification. In most scenarios, you do not want to set the <code>host</code> field.
Here&rsquo;s one scenario where you would set it. Suppose the Container listens on 127.0.0.1
and the Pod&rsquo;s <code>hostNetwork</code> field is true. Then <code>host</code>, under <code>httpGet</code>, should be set
to 127.0.0.1. If your pod relies on virtual hosts, which is probably the more common
case, you should not use <code>host</code>, but rather set the <code>Host</code> header in <code>httpHeaders</code>.</p>

















<h2 id="what-s-next">What&#39;s next</h2>
<ul>
<li>Learn more about
<a href="../../../user-guide/pod-states/index.html#container-probes">Container Probes</a>.</li>
</ul>

<h3 id="reference">Reference</h3>

<ul>
<li><a href="../../../reference/generated/kubernetes-api/v1.11/index.html#pod-v1-core">Pod</a></li>
<li><a href="../../../reference/generated/kubernetes-api/v1.11/index.html#container-v1-core">Container</a></li>
<li><a href="../../../reference/generated/kubernetes-api/v1.11/index.html#probe-v1-core">Probe</a></li>
</ul>






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